The major objective of this research project is to elucidate the neural organization of the primate oculomotor system at the cellular level. Microelectrodes are used to record the activity of single neurons in the brainstem of fully alert, behaving monkeys. Unit activity is correlated with eye movement parameters (measured with a sensitive, drift-free magnetic field method of measuring eye movements) and with visual and vestibular sensory stimulation. The current work focuses on the neuronal basis underlying the coordination of eye and head movements. A class of neurons located in the pontine reticular formation has been shown to burst prior to saccadic eye movements, but the parameters quantifying this discharge are only crudely related to saccade metrics. Our preliminary results show that much of the variability in discharge in these units may be related to simultaneous head movements. The quantitative relationship between the discharge of these reticular units and coordinated eye and head movements will be established in the present project.